Femtosecond lasers create 3D midair plasma displays you can touch (2015) | Hacker News Reader

Femtosecond lasers create 3D midair plasma displays you can touch (2015)

spectrum.ieee.org

284 pointsjagged-chisel141 comments

I have a slight eye damage in one eye from working with lasers that were just a bit outside the safe limits. And I realized that only years after getting it.

So the last thing I want, is to be near unconfined lasers powerful enough to ionize the air.

How did you realized you had eye damage?

check engine light in the upper left hand corner of his vision.

Typically you'll notice a persistent black spot in your vision. Particularly if you're looking at a bright field like a blank white page on your monitor.

Cite? My vague understanding of how vision works is that your brain will tend to interpolate over missing data rather than perceive it as black. So you need to actually test whether you can discriminate things in the affected field of view.

Vision is complicated. Everyone's vision experience is slightly different. So different people might notice different things.

This is not a citation, but...

I have this spot in my right eye that resembles dead pixels. Just tiny blackness. If I let my eyes try to focus on it, it moves with my eyeball, so then they try to focus on the new location... ad infinitum. So they sort of jitter on a path upwards and to the right. I can only see it in certain lighting.

Eye doctor couldn't see anything wrong with the area and suggested it might be a floater that got attached and would go away on its own within 6mo. That was 4yr ago and it's still around. It's not getting worse so it doesn't bother me, it just reminds me of the saa from the Wheel of Time.

I would have expected interpolation versus vision artifacts as well, but apparently that's an "only sometimes" thing.

You have a speck of gunk in your vitreous near the focal point. Not retina. You can’t ‘see’ damage to your retina… you brain just interpolates. The gunk in your vitreous can stay there a long time… it’s gel, more or less, and can take a long time to move.

My dad has quite a severe spot where his retina detached in the one eye. Right in the centre of his vision.

He reports it looking like a visible hole with surrounding distortion. Apparently similar to some renderings of black holes.

That said, this is a large defect in the centre of vision - it's pretty much un-interpolatable.

I understand smaller defects not in the macula just get interpolated away.

You're asking for a citation for someone describing their personal experience?

The comment by utensil4778 I am replying to made a generalization and did not mention their personal experience (although the phrasing maybe suggested that their experience was consistent with the general claim).

Generally, yes. That's why people tend to go for quite a while before noticing the damage.

The mechanism isn't perfect and there are plenty of scenarios where your brain doesn't fill in the information, like the one I described. You also see it when looking at repeating patterns. It isn't something super obvious and if you choose to ignore it, it mostly goes away.

If your brain magically filled in the missing part of your vision in all cases, ask yourself how we would ever know that anyone has any amount of damage to their vision. Obviously we do know, since people talk about it. There must be some mechanism by which the damage becomes apparent to the patient.

Don't know how OP did it, but I've been tested a couple of times at the optometrist by field of view machines*. You concentrate on a central point while the machine shows you a pictogram in a random location with a random timing. You click a button every time you see one.

Note: not an actual name, I don't know how these are called.

I believe the machine you're referring to is called a Humphrey visual field analyzer.

https://en.wikipedia.org/wiki/Humphrey_visual_field_analyser

These tests are no fun at all.

If I look at a straight line with the right eye, I see a "kink" in it. Grids look like they are warped in near the center.

Turns out, that I have a "pinhole" damaged area in the right eye's fovea. It's small enough that the brain can "interpolate" over it, especially when both eyes can see the object.

Gee, if only they had thought of this rather obvious point and addressed it in the article.

I think the same happened to me with LEDs. I have an odd feeling that I can't really see a small section somewhere close to the center of focus, not directly at it. I remember an odd sensation in the eye for days after dealing with a white LED.

Are you sure thats not just the blind spot? It's quite big - roughly the size of a rubbish bin lid on the other side of a bedroom.

Here's how to spot it:

Hold you hands together, with thumbs up, at arms length. Close your left eye, and slowly move your right thumb away to the right, while looking at your left thumb. At around 6 inches it will dissapear.

It's kind of hard to notice when my thumb is static, but it's more obvious if I wiggle my thumb while doing it.

Woah, that's neat!

Wow, cool stuff! But no, its much closer to the center, and it's not something I can really spot. I just know that it started after I dealt a bit with newly bought "high power" leds. Not really high power and I never really looked directly into them (them facing at me). It also might have been some bright, red ones on breadboards. Happened over 10 years ago.

Optometrists have cameras that can take pictures of your retina and see if there's any obvious damage. You might consider getting your eyes checked out.

They won't see "dead pixels" unless it's severe damage, or a different underlying cause. All bets are off on the optical nerve, since MRI resolution may at best allow to spot a tumor.

They can, however, do an extended version of the blind spot experiment above for the whole field of vision, where they project light dots into a hemisphere in an unpredictable but iteratively somewhat exhaustive fashion. Very tiring and challenging test, since you need to keep your eyes from wandering, fixated at a boring reference point for more than half an hour. Like a hearing test, but for your eyes...

Laser beams or high energy radiation in general may also damage vision elsewhere in the optical pathway. Like opacification in the cornea or vitreous body when proteins get denatured by the heat. The body is very bad a repairing any damage in the optical apparatus since the eyes do have their own blood barrier, so macrophages usually don't have access to clean up "junk", and most tissues involved aren't really regenerative. Worse, damaged proteins tend to slowly spread the faulty structure to their neighbors.

Don't fuck with your eyes!

You may be able to better pin it down along sharp contrast lines, maybe moving, or flickering patterns. Eg. a black and white grid, stripes, or small checkerboard pattern on an LCD screen. And of course isolate eyes for these tests.

Your brain can fill in a lot of voids before you notice, especially for monotonous areas and static impressions (as mentioned the blindspot or the blood vessels on your retina are usually "invisible" until you provoke awareness through unusual lighting changes, or defined peripheral accounting experiments). You likely won't notice acquired "blindspots" looking at a white wall, or chaotic fallen leaves on the ground, especially where the other eye provides missing information, but at the edges of highly predictable patterns, one eye closed at a time, you may trick your brain to fuck up, eg. blur or indent otherwise clearly defined areas, when it can't decide which color to fill. Reading texts with on eye closed may also highlight "dancing" letters or distortions around your center of vision.

Worth noting, such defects may be caused by progressive conditions like retina detachment or even ocular melanoma, and the association with laser/light accidents may be incidental. If you spot a spot, do not brush it off as a limited loss! Have it checked, even with a likely attributable cause. You may prevent full blindness through medical intervention in case of disease!

Edit: You can see the blood vessels when you look a white wall and steadily move a (smartphone) flashlight in and out of the field of vision, slowly waving the light next to your head, illuminating from your ears to the side of your nose and consequentially your eyes at a shallow angle. This will cause an unusual blood vessel shadow, now meandering through your vision. The blood vessels are also very visible during eye examinations when the doctor moves the slit lamp around (go check it out ;)

Very weird seeing the insides of the very eye seeing, by ... well ... seeing.

Some of my earliest memories are of these kinds of perception, including the 'phosphenes' caused by internal pressure on the eyes when one looks to the side (they appear as fleeting, roundish flashes). It's curious to me that such formative memories would be triggered by something entirely 'internal' - not a measure of external stimulus involved. Perhaps in a similar way, someone else's earliest memory might be that of becoming aware of their heart beating!

I don't think there is much of a brain when the heart starts beating.

Edit: Never mind; misread.

I’d be surprised if you damaged your eyes with any LEDs in the visible spectrum. Walking around in midday sun exposes you to orders of magnitude more energy. Maybe if you had focusing lenses on them, and they were really high power, like the kind that needs heat sinks to operate safely.

If you had say UV LEDs, all bets are off since it wouldn’t trigger the pupillary light reflex to close down the iris.

Some white LEDs are actually near-UV LEDs coated with a phosphor layer to emit visible wavelengths. Could be GP got LEDs with poor coating allowing UV through?

The visible component would still cause your eye to narrow the pupil.

Try to map out the spot:

Make a grid in a drawing program with crosshairs in the centre. Close one eye. Keep looking at the crosshairs. Scan from the central focus point using your mouse and click when you can't see the mouse cursor. With a bit of trial and error you should be able to map out large regions you can't actually see in.

(My dad did this years ago for a retinal detachment spot in his one eye.)

More importantly: get an optometrist to check out your retina.

That's really cool. I tried it with an angled mirror, it was really weird wiggling my thumb and seeing it in the reflection but not outside of it.

I have a similar thing. Have had numerous tests for it, and no one (so far) has been able to give me a satisfying explanation. I've gotten used to it, but it freaked me out when I first noticed it.

Warning: Do not touch laser with remaining hand.

not that one, the other one.

> So the last thing I want, is to be near unconfined lasers powerful enough to ionize the air.

I wholeheartedly agree. Just thinking about how the potentially-unregulated cheaply-manufactured knock-off projectors will result in having to wear welding glasses when walking around the street to avoid being blinded by the 3D advertisements that are being shot at your face...

Unfortunately, we couldn't even protect the dumbs from staring at a solar eclipse. Safety standards are ridiculously hard to calibrate.

Unrelated, how bad is it to look without protection during totality? We got the approved eclipse glasses and diligently kept them on through the whole lead-up, then couldn't see shit once totality started, so we took them off and gazed at the loveliness and then hastily put them back on t moment the sun started to re-emerge.

I get that it's not good to tell the public "don't look at an eclipse unprotected except for this precisely-timed period," because that would lead to a statistically significant increase in permanent eye damage, but what we did seems to have gone fine, at least when exposures are circa once a decade.

The general advice (at least from everything I've seen) is that you can and should remove your eclipse glasses during totality; after all, the bright surface of the sun is totally blocked.

I personally looked into the research on solar eye damage a few years ago (when the 2017 eclipse fervor had died down), and my impression is that all recorded cases result from focusing directly at the sun for at least several seconds straight; glancing very briefly at the sun, or seeing it in your peripheral vision, is only uncomfortable at worst. Eye damage is mainly associated with eclipses since they motivate many people to stare at the sun, rather than the partially-eclipsed sun being uniquely dangerous to look at. But when the time comes around, the messaging gets very black-and-white, as you said.

(Not that it's a bad idea to avoid looking at the sun as much as possible!)

I've also been interested in this in the past since I slightly damaged my eye by staring at a partial eclipse as an adolescent. (I can no longer perceive any damage, but it might have permanently reduced my retinal acuity in one spot.)

> Eye damage is mainly associated with eclipses since they motivate many people to stare at the sun, rather than the partially-eclipsed sun being uniquely dangerous to look at.

Most sources seem to agree with that, and that's basically my impression. But I do know of another theory, which is that damage is associated with something like J/m² absorbed energy, and so roughly with (W/m² × s) of exposure, but the blink or discomfort reflex is associated with something more like total W entering the eye. The way that the sun is obscured during a partial eclipse is not by dimming (which would reduce both the total power entering the eye and the total power absorbed by a given region of the retina by the same factor), but instead by making a portion of the solar disc invisible, while leaving other portions fully visible. Those portions are still causing a comparable absorption of energy per second on the parts of the retina where they are focused, but the partially-obscured sun, in addition to being much more interesting, might be less uncomfortable to stare at because of the total amount of light being lower.

Sorry if that account was too wordy. A more concise way of putting it might be: Your desire to look away after a relatively short time is based on the total amount of light entering your eye (which is reduced during a partial eclipse), but the sun's ability to damage your eye is based more on the total amount of light focused on a given part of your retina (which is not reduced very much, since the parts of the sun you can still see are just about as bright as usual).

I don't know whether that interpretation is right, but it's another wrinkle on the "you're more inclined to stare at the sun during an eclipse than you usually would be" issue: it might not be exclusively because it's more interesting, but also because the total light is less than usual, so your discomfort is less than usual, but your risk of injury per second is only very slightly decreased.

Related to this, we don't have pain receptors directly on the retina itself, so the feeling of discomfort we get when looking at a bright light isn't directly indicating whether the retina is being damaged or not.

Don't our eyes adjust, so if it seems like the sun is obscured the pupils would dilate increasing potential damage?

That's also an issue for some scenarios, but if you're looking directly at the sun (even partly obscured), your pupils are probably already as small as possible!

UV light is not visible, but it is high energy electromagnetic waves.

Your brain doesn't process "excess light" because your eyes aren't sensing visible light. They are being exposed to damage by the rest of the light, nonetheless.

Yes, but I don't think there's more UV during an eclipse (even in proportion to visible light). Overall, there should be less UV than there would be from viewing the full sun.

The issue you mention does come up if you have a filter that blocks visible light but not UV. Non-UV-blocking sunglasses, for example, could increase the risk of cataracts compared to not wearing sunglasses at all (mainly because of pupil dilation).

Thanks for elaborating! I remembered hearing something to that extent back in 2017, but after I couldn't find any primary sources on it online, I'd dismissed it as a rumor. Absolute duration would still be the primary factor, in any case.

Luckily I've never had any eye problems myself, but not for lack of trying. Back in elementary school, I would occasionally stare at the outdoor sun for 30 seconds or longer, just to see what could possibly be so bad about it.

Yet my eyes remain undamaged, at least as far as any optometrist has told me. Hence why I was skeptical about the supposed danger of eclipses. But perhaps the interval before damage can be much shorter, depending on age and other factors.

I think there are probably factors like

* latitude

* time of day¹

* individual genetics (maybe including something about the anatomy of your iris? or the focal abilities of your eye?)

* how fixedly you manage to stare at the sun, as opposed to letting your eye wander around a bit

* how frequently you unconsciously blink

that would cause the degree of injury to vary a lot. But it's understandable that experts would like to emphasize the really, just don't stare at the sun principle as the most reliable advice, so people don't do a lot of second-guessing (like "oh well I'm at a high latitude so it's not that bad").

I had also stared at the sun a little bit on occasion in elementary school (but for like 4-5 seconds, not like 30 seconds!) and that was one thing that gave me some counterproductive confidence that it wouldn't be super-harmful super-quickly.

¹ Notably, a lot of people will "watch the sunset" for like 1-5 minutes at a time, which is a form of starting at the sun, and I've never heard of that causing anyone any trouble. It really is true that time of day and latitude both have a big effect on the intensity of sunlight. Among other things, this interactive diagram makes pretty clear why watching the moment of sunset isn't that dangerous: https://engaging-data.com/solar-intensity/

It's easy to confirm there that the incident power in direct sunlight can vary by a factor of 100× as you get further from the tropics and closer to the moment of sunrise or sunset.

But it's not a great risk to have lots of people apply these heuristics to justify staring at the sun. If you just get a little bit confused about the details, the potential for damage is very, very high!

As I like to say, it's funny that humans are the one and only member of the animal kingom who must be told not to stare at the sun.

Failing to look at totality during an eclipse because of too coarse public health guidelines (predicated on the fact that you're an idiot) is tragic.

During totality, there is no danger to your eyes to looking directly at the corona. You can tell on account of how it isn't bright.

> result in having to wear welding glasses when walking around the street to avoid being blinded by the 3D advertisements that are being shot at your face...

but I'm sure the welding glasses would fit the overall cyberpunk aesthetic of that future very well

And once everyone's walking around wearing welding masks, the dorky look of AR goggles will no longer hold back mass adoption.

This article is 9 years old. Probably went nowhere because of the reason you state.

Lol, I completely missed this. Thanks for the callout. That WAS right around when everyone was trying to (or started to) use gimmicky volumetric displays at the trade shows I attended.

What sort of work? Industrial processes like cleaning or cutting, or physics/engineering bench firing?

Physics (well, physics for microbiology), with IR and red lasers. I was pretty diligent with wearing glasses, but apparently not diligent enough.

Sometimes there's no way to be safe, e.g. aligning pumped lasers where you'd need one set of glasses for the pump wavelength and another for the final wavelength.

> The researchers found that a pulse duration that minuscule doesn't result in any appreciable skin damage unless the laser is firing at that same spot at one shot per millisecond for a duration of 2,000 milliseconds

Haha so if this thing is misconfigured badly enough it can just melt you

How much does an 0-day cost for a device that can literally kill?

Ask an automaker or an airline

Boeing's hitman could not be reached for comment.

I hear they will pay a visit though if you hashtag "whistleblower" and "Boeing"

Do they just show up and remove all your door hinges?

That’s very awkward wording. Is it saying a 1ms pulse every 2s?

I understand it as one pulse (shorter than a ms) each ms for 2 seconds.

fs pulse duration, 1ms repetition rate, 2s run duration

It'll engrave you. The spot size is small and the material removal rate is low.

Still not fun, but it's not gonna take a finger.

Sounds like a promising topic for an Electroboom video.

> Still not fun, but it's not gonna take a finger.

It might take your retina though

This technology came up recently in conversation so I searched the web to see what became of it. All I can find are articles dating from summer 2015 and nothing of substance after that.

I’m sure we can all come up with some reasons this wouldn’t be practical in many situations, but the tech seemed promising. Do any of you have knowledge of what happened here? Was it smoke and mirrors? Just really not practical? I would really like to read some details about why this seems to have vanished.

Go into a lab in the first floor of the physics building at my Uni and you are likely to find a femtosecond laser inside which sprawls over an optical bench which takes up most of the room. At the heart of it is a fiber laser that costs about $250,000 but they usually have added a lot of stuff to it.

A femtosecond laser for medical use is about $400,000

https://crstoday.com/articles/2014-sep/pricing-the-laser-cat...

which is one reason you might not see this become widespread.

Ironically that seems promising. This could just be an engineering problem where the only people making the required laser equipment are only making lab/medical grade gear with enormous markups. It's possible someone comes up with a practical to manufacture solid state version that unlocks these displays for the masses.

There is one consideration however where one failure mode for this device includes a situation where the processing locks up and leaves the laser pointed at a single spot continuously, burning a hole and possibly starting a fire.

> where the processing locks up and leaves the laser pointed at a single spot continuously, burning a hole and possibly starting a fire.

Already solved for 3d-printers locking up and starting a fire.

Lasers used for laser light shows already have interlocks that will stop the laser if the mirror stops moving.

My understanding is that femtosecond lasers have some parts that are physically large because they use prisms, diffraction gratings, and such, to spread out a pulse so the laser can effectively amplify it and then recompress the pulse to use it.

See

https://en.wikipedia.org/wiki/Pulsed_energy_projectile

note a workable laser "gun" could plausibly be "set to stun" because if the energy of a pulse sparks the air near your skin or clothing, the plasma absorbs almost all the energy causing a plasma explosion which can knock you down plus cause severe pain from an electromagnetic pulse.

The pulses are not entrained to software. They are inherent to the laser's design, such as with Q-switching.

I think ops point still holds - actively modulated q switches could still have a failure that pushes the laser outside the safety parameters, no? I don’t think OP was necessarily suggesting a software failure.

Q-switching does not operate like a transistor's base. It is more like the charge pump on a camera flash. It will not produce a high-power pulse if operated outside of parameters. There are other ways with different physics but comparable principles.

I'm incredibly curious as to what that even looks like. Where do you study? Can you give us a photo?

See

https://www.oist.jp/image/researchers-femtosecond-spectrosco...

https://www.mp.aau.dk/research/laboratories/physics-lab/shor...

https://hajim.rochester.edu/optics/sites/guo/virtual-lab.htm...

Seems like the tech is still likely alive and kicking in the military space: https://patents.google.com/patent/US20200041236A1/

US Navy submitted a patent in 2018 for a jet-mounted plasma decoy projector, I'm sure they have many more applications that I wasn't able to find as well

> the tech is still likely alive and kicking in the military space

I mean, it's a field that burns things that wander into it. I'm genuinely blown away this was considered for a display technology. It's closer to the risk profile of fireworks than an OLED.

Remember all those UFOs people were reporting? That was probably this, military took it over.

> laser-induced plasma displays that ionize air molecules to create glowing points of light.

The New Scientist used to have a column inside the back page called Daedalus. It usually described some kind of weird or wonderful "invention" that probably wasn't practical. One of them was for street lighting: you'd have pairs of ultraviolet lasers on either side of the street, intersecting in mid-air. The pairs of lasers would have frequencies that were not exactly the same, so that at the point of intersection lower-frequency "beats" would occur. If the frequency of the beats were adjusted to match the excitation energy of (e.g.) O2, the oxygen would emit light.

Another Daedalus "invention" I remember was to use plant tropins to control the growth of wood. You could then grow e.g. an armchair, or a table, or even a house. No glue needed, no saw needed.

I don't know who used to write that column.

Controling the growth of wood in that manner is a pretty common fantasy trope, usually of the Elven variety. Or treesinging in Wheel of Time, for example. It's one of those that occasionally pops into my head. Would be pretty neat from a CO2-sequestration point of view, but unless the wood is stressed appropriately during growth, the resulting furniture (or housing) would likely crumble pretty easily.

Bending young trees and keeping them in place mechanically to make them grow into interesting or useful shapes is quite viable, probably not to make an armchair but possibly pieces for constructing one, or something simple, like a one-piece walking stick.

Here's a company that make such chairs: https://fullgrown.co.uk/

Interesting, thanks.

> something simple, like a one-piece walking stick

Something like this? Except that it's not had its growth manipulated, either by tropins or mechanical means (it was coppiced though).

https://www.emilyhannah.co.uk/wooden-walking-sticks/knob-sti...

Looks nice, but no, I was thinking more like bent into a handle.

I was thinking the other day if lab grown wood would be viable, like lab grown meat.

Maybe genetically engineered trees that all grow in nominal dimensions like Minecraft trees.

Reminds me of the story from a few years ago where the US military was looking into scaring people via screaming balls of plasma, which gave rise to the joke that the CIA was trying to make religious extremists think their god was talking to them using the tech.

https://newstarget.com/2018-04-24-u-s-military-creating-non-...

I remember this! I'm glad someone else does too.

Weren't these things ear-splittingly loud from the constant formation of plasma balls in midair? That's what I recall from a demonstration In The Day

Looking into the plasma/laser paper and it mentions 77.2 dB at an insanely close 22mm distance. Background was 55.7. http://arxiv.org/pdf/1506.06668v1 Page 9.

It sounds (hah) like it wouldn't be pleasant if you have your head near a full display in operation, especially since the noise scales with the resolution/brightness. It would be interesting to see how quickly the noise drops off over distance. You are looking at something between a home sound system, vacuum cleaner, or highway traffic at that volume level. Tolerable but not pleasant.

I wonder if it could be modulated to function as a sound system?

Yes.

You may enjoy the similar use of Tesla coils: https://youtu.be/rd3bH_xNYYQ?si=TXO_kA0PZ6YkUZyt

Personally I'm more the floppy drive fan.

https://m.youtube.com/watch?v=8fh1CIupVXU

But Tesla coils are cool, as are van de graaff generators.

A friend of mine built speakers that ionized the air and then used some mechanism (electrostatics? voice coil?) to move the air directly; kind of a coneless speaker. It didn't get that loud and made a lot of ozone.

I remember IO2 Heliodisplay from around 2007. Now their site seems to be dead.

> This holographic-style display works by projecting a 2D image onto a cloud of microscopic droplets (probably water, although this isn't confirmed)

https://www.techpowerup.com/forums/threads/io2-launches-%E2%...

I followed them for ages, such cool tech for the early 00s when they first publicised it. But it never seemed to have gone anywhere.

They were very cagey at first about the fact it used water vapour because they didn’t want people to think it was just projection onto a vapour screen when they had some sort of directed laser tech. It still needed the water though!

If I were to guess why it didn’t reach any sort of momentum, I reckon they couldn’t control the costs or get the brightness good enough. But that’s really speculation.

This is quite hard to do safely. Generating air breakdown with IR femto requires a reasonable amount of fluence. They are probably using galvo scanners to shift the beam in xy, but to get the required intensity they have to also shift the focal plane. Given the distances they are projecting away from the car that NA is low meaning they would need a reasonable power. Probably why they are running it at 1kHz. Given its 2015 it is probably a ti-sapphire at 80fs, galvos and an optotune lens. The reason this isn't a thing is that it very hard to make this eye safe.

I often wonder the same about the technology used in a mysterious video that appeared on youtube about 15 years ago titled "Laser Induced Plasma Channel".

It appears to be an area denial weapon that uses femtosecond lasers to guide electric arcs across a hallway (think a metre-long ridiculously straight Taser discharge).

The video had no description and comments on it were never answered - it was recently removed by the uploader, but there seems to be a reupload on DailyMotion[1] from 9 years ago.

[1] https://www.dailymotion.com/video/x31ovvi

If you're interested in that project.

Here is an equally cool project form Voxon Photonics. That you can buy today and is also very safe.[0]

[0]: https://voxon.co/

There are many display technologies that just didn't make it to mass production.

A favourite of mine is Field Emission Display technology. However they are largely irrelevant now because OLED essentially fill the same role.

Mine is transreflective LCD. I just really want to be able to work with my laptop in the sun.

https://en.wikipedia.org/wiki/Transflective_liquid-crystal_d...

Here it's used on the Adam Tablet that never took off: https://www.youtube.com/watch?v=pGUKHDBoTEc

LTT just made a video about a modern display that is like this tech https://www.youtube.com/watch?v=c0TcGjzKbag

Interesting! Although going for no backlight seem to make it about as impractical indoors as regular displays are outdoors?

Hi had an Adam, the idea (and display) was pretty cool, but the build quality and software was not that great. Eink really has taken over that niche though, so not sure I really miss those displays.

Yeah it seems that TLCD never really got a chance to get developed properly.

And Eink seem to me to have a lot of other clear drawbacks which makes it impractical for regular work use cases.

We played with lenticular displays and they are very good and very safe. But like it's just not that useful to have a 3d display. A 2d screen is perfectly good at conveying the same information.

They're thermally heating up the air with lasers?

Doesn't a white-hot atmospheric plasma emit plenty of hard UV?

Or is this some kind of specific spectral line emission that the photos don't do justice?

OP forgot to include it in the title, but this is from (2015).

See-through displays show up in movies so that the viewer can see the actors' faces. Not because see-through displays are useful.

You can also use femtosecond lasers and a streak camera to film the speed of light: https://www.youtube.com/watch?v=7Ys_yKGNFRQ

Maybe one day something like this can be used to have true light-field cameras without microlens arrays (like Lytro had).

This page has been around for a while. If you watch the YouTube video, you can see the skin on the person’s finger get burnt as they touch the little tiny plasma balls.

https://youtu.be/AoWi10YVmfE?si=1zzwNba9A1l9Y2ld

> it’s not that crazy to look at this project and believe that such a gadget* might not be so far away.

9 years later, I think we can safely say yes, it is crazy to believe that such a gadget might not be so far away.

*quotation was referring to wearable holographic displays made with this tech

This was supposed to be Ask HN but I didn’t realize I was on the wrong page for Ask submissions. So the title was changed to reflect the article. Anyway, my comment asked the question and we got some discussion, so it’s all good.

Very cool!

How energy efficient could it theoretically be? Is it somewhat relatable to touchscreens, or are we talking thousands of times more power per pixel per second?

Worth calling out this article is from 8 years ago.

Whatever happened to the idea of sending electricity through air with this technology?

One application I heard of in the 90s was a long range taser.

The video shows slightly burned skin on the tip of his finger where he has been touching the "display".

I just want to point out holodeck episode in Star Trek preceded Star Wars by 3 years.

It was the animated series, if anyone else is like me and could not for the life of themselves remember a holodeck in the original series (Thanks Memory Alpha!).

I’m imagining blade runner style giant holograms above buildings if this tech matures

That's it, we've got holograms now. So cool!!!! :) Hahaha! :)

While we're on the subject, what happened to uBeam?

same thing that happened to theranos, just in a lower-key fashion; they hadn't figured out how to do the thing they said they'd figured out how to do, and possibly nobody ever will

in my book that makes them a fraud, though there are clearly a lot of ai company founders who disagree

They collapsed, because they couldn't deliver anything remotely close to what was promised. IMO they knew all along it was a fraud and just kept the story going as long as they could.

I think they renamed themselves "sonic energy". Excellent thread on eevblog:

https://www.eevblog.com/forum/chat/the-ubeam-faq/1900/

Now Perry is pumping some neuro-ai-sleep-aid nonsense.

How much NOx would this generate, I wonder.

Until a kid put his face in it for fun

(2015)

Ctrl-F ozone - nothing. Hello cancer my old friend.

the large kind also do this in a sense

(2015)

Que ads.

(2015)

> However, a nanosecond-scale plasma burst still contains a significant amount of energy; you don’t want to go walking through one of these displays, because it will burn you.

Yeah, i think that answers the headline question. Burning people is bad.

So will touching a lightbulb, but we have those in abundance in the same application. I don't think that adequately answers the question.

We don't usually have lightbulbs suspended mid-air at human height without some sort of protective case.

I guess i assume the point here is to have no protective case since the article made such a big deal about touching the display.

The overwhelming majority of lights are within human reach with no protective casing. There might be a lampshade to diffuse the light, and some frame to physically support the bulb, but nothing to stop a human hand from reaching in and touching it. Hell installing and replacing bulbs is typically done with bare hands. Free hanging bulb lights used to be quite common in closets and basements.